forked from OSchip/llvm-project
[JumpThreading] Add a pattern to TryToUnfoldSelectInCurrBB()
Add the following pattern to TryToUnfoldSelectInCurrBB() bb: %p = phi [0, %bb1], [1, %bb2], [0, %bb3], [1, %bb4], ... %c = cmp %p, 0 %s = select %c, trueval, falseval The Select in the above pattern will be unfolded and then jump-threaded. The current implementation does not allow CMP in the middle of PHI and Select. Differential Revision: https://reviews.llvm.org/D34762 llvm-svn: 308050
This commit is contained in:
Haicheng Wu
parent
302a9d41c6
commit
476adcca6b
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@ -2168,11 +2168,19 @@ bool JumpThreadingPass::TryToUnfoldSelect(CmpInst *CondCmp, BasicBlock *BB) {
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return false;
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}
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/// TryToUnfoldSelectInCurrBB - Look for PHI/Select in the same BB of the form
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/// TryToUnfoldSelectInCurrBB - Look for PHI/Select or PHI/CMP/Select in the
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/// same BB in the form
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/// bb:
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/// %p = phi [false, %bb1], [true, %bb2], [false, %bb3], [true, %bb4], ...
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/// %s = select p, trueval, falseval
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/// %s = select %p, trueval, falseval
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///
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/// or
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///
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/// bb:
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/// %p = phi [0, %bb1], [1, %bb2], [0, %bb3], [1, %bb4], ...
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/// %c = cmp %p, 0
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/// %s = select %c, trueval, falseval
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//
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/// And expand the select into a branch structure. This later enables
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/// jump-threading over bb in this pass.
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///
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@ -2186,44 +2194,54 @@ bool JumpThreadingPass::TryToUnfoldSelectInCurrBB(BasicBlock *BB) {
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if (LoopHeaders.count(BB))
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return false;
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// Look for a Phi/Select pair in the same basic block. The Phi feeds the
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// condition of the Select and at least one of the incoming values is a
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// constant.
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for (BasicBlock::iterator BI = BB->begin();
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PHINode *PN = dyn_cast<PHINode>(BI); ++BI) {
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unsigned NumPHIValues = PN->getNumIncomingValues();
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if (NumPHIValues == 0 || !PN->hasOneUse())
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// Look for a Phi having at least one constant incoming value.
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if (llvm::all_of(PN->incoming_values(),
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[](Value *V) { return !isa<ConstantInt>(V); }))
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continue;
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SelectInst *SI = dyn_cast<SelectInst>(PN->user_back());
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if (!SI || SI->getParent() != BB)
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continue;
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Value *Cond = SI->getCondition();
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if (!Cond || Cond != PN || !Cond->getType()->isIntegerTy(1))
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continue;
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bool HasConst = false;
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for (unsigned i = 0; i != NumPHIValues; ++i) {
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if (PN->getIncomingBlock(i) == BB)
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auto isUnfoldCandidate = [BB](SelectInst *SI, Value *V) {
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// Check if SI is in BB and use V as condition.
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if (SI->getParent() != BB)
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return false;
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if (isa<ConstantInt>(PN->getIncomingValue(i)))
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HasConst = true;
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Value *Cond = SI->getCondition();
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return (Cond && Cond == V && Cond->getType()->isIntegerTy(1));
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};
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SelectInst *SI = nullptr;
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for (Use &U : PN->uses()) {
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if (ICmpInst *Cmp = dyn_cast<ICmpInst>(U.getUser())) {
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// Look for a ICmp in BB that compares PN with a constant and is the
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// condition of a Select.
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if (Cmp->getParent() == BB && Cmp->hasOneUse() &&
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isa<ConstantInt>(Cmp->getOperand(1 - U.getOperandNo())))
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if (SelectInst *SelectI = dyn_cast<SelectInst>(Cmp->user_back()))
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if (isUnfoldCandidate(SelectI, Cmp->use_begin()->get())) {
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SI = SelectI;
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break;
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}
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} else if (SelectInst *SelectI = dyn_cast<SelectInst>(U.getUser())) {
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// Look for a Select in BB that uses PN as condtion.
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if (isUnfoldCandidate(SelectI, U.get())) {
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SI = SelectI;
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break;
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}
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}
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}
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if (HasConst) {
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// Expand the select.
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TerminatorInst *Term =
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SplitBlockAndInsertIfThen(SI->getCondition(), SI, false);
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PHINode *NewPN = PHINode::Create(SI->getType(), 2, "", SI);
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NewPN->addIncoming(SI->getTrueValue(), Term->getParent());
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NewPN->addIncoming(SI->getFalseValue(), BB);
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SI->replaceAllUsesWith(NewPN);
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SI->eraseFromParent();
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return true;
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}
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if (!SI)
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continue;
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// Expand the select.
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TerminatorInst *Term =
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SplitBlockAndInsertIfThen(SI->getCondition(), SI, false);
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PHINode *NewPN = PHINode::Create(SI->getType(), 2, "", SI);
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NewPN->addIncoming(SI->getTrueValue(), Term->getParent());
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NewPN->addIncoming(SI->getFalseValue(), BB);
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SI->replaceAllUsesWith(NewPN);
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SI->eraseFromParent();
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return true;
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}
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return false;
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}
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@ -287,3 +287,78 @@ cond.false.15.i: ; preds = %cond.false.10.i
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; CHECK: br i1 %phitmp, label %.exit.thread, label %.exit.thread2
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; CHECK: br label %.exit.thread2
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}
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define i32 @unfold4(i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z, i32 %j) nounwind {
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entry:
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%add3 = add nsw i32 %j, 2
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%cmp.i = icmp slt i32 %u, %v
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br i1 %cmp.i, label %.exit, label %cond.false.i
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cond.false.i: ; preds = %entry
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%cmp4.i = icmp sgt i32 %u, %v
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br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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cond.false.6.i: ; preds = %cond.false.i
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%cmp8.i = icmp slt i32 %w, %x
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br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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cond.false.10.i: ; preds = %cond.false.6.i
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%cmp13.i = icmp sgt i32 %w, %x
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br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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cond.false.15.i: ; preds = %cond.false.10.i
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%cmp19.i = icmp sge i32 %y, %z
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%conv = zext i1 %cmp19.i to i32
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br label %.exit
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.exit: ; preds = %entry, %cond.false.i, %cond.false.6.i, %cond.false.10.i, %cond.false.15.i
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%cond23.i = phi i32 [ 1, %entry ], [ 0, %cond.false.i ], [ 1, %cond.false.6.i ], [ %conv, %cond.false.15.i ], [ 0, %cond.false.10.i ]
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%lnot.i18 = icmp eq i32 %cond23.i, 1
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%j.add3 = select i1 %lnot.i18, i32 %j, i32 %add3
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ret i32 %j.add3
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; CHECK-LABEL: @unfold4
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; CHECK: br i1 %cmp.i, label %.exit.thread, label %cond.false.i
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; CHECK: br i1 %cmp4.i, label %.exit.thread3, label %cond.false.6.i
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; CHECK: br i1 %cmp8.i, label %.exit.thread, label %cond.false.10.i
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; CHECK: br i1 %cmp13.i, label %.exit.thread3, label %.exit
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; CHECK: br i1 %lnot.i18, label %.exit.thread, label %.exit.thread3
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; CHECK: br label %.exit.thread3
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}
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define i32 @unfold5(i32 %u, i32 %v, i32 %w, i32 %x, i32 %y, i32 %z, i32 %j) nounwind {
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entry:
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%add3 = add nsw i32 %j, 2
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%cmp.i = icmp slt i32 %u, %v
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br i1 %cmp.i, label %.exit, label %cond.false.i
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cond.false.i: ; preds = %entry
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%cmp4.i = icmp sgt i32 %u, %v
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br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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cond.false.6.i: ; preds = %cond.false.i
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%cmp8.i = icmp slt i32 %w, %x
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br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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cond.false.10.i: ; preds = %cond.false.6.i
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%cmp13.i = icmp sgt i32 %w, %x
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br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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cond.false.15.i: ; preds = %cond.false.10.i
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%cmp19.i = icmp sge i32 %y, %z
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%conv = zext i1 %cmp19.i to i32
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br label %.exit
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.exit: ; preds = %entry, %cond.false.i, %cond.false.6.i, %cond.false.10.i, %cond.false.15.i
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%cond23.i = phi i32 [ 2, %entry ], [ 3, %cond.false.i ], [ 1, %cond.false.6.i ], [ %conv, %cond.false.15.i ], [ 7, %cond.false.10.i ]
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%lnot.i18 = icmp sgt i32 %cond23.i, 5
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%j.add3 = select i1 %lnot.i18, i32 %j, i32 %cond23.i
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ret i32 %j.add3
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; CHECK-LABEL: @unfold5
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; CHECK: br i1 %cmp.i, label %.exit, label %cond.false.i
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; CHECK: br i1 %cmp4.i, label %.exit, label %cond.false.6.i
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; CHECK: br i1 %cmp8.i, label %.exit, label %cond.false.10.i
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; CHECK: br i1 %cmp13.i, label %.exit, label %cond.false.15.i
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; CHECK: br label %.exit
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}
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